1. Field of the Invention
The present invention relates to a vibratory gyroscope, and particularly, to a vibratory gyroscope comprising a vibrating body and two detecting piezoelectric elements which are formed on the vibrating body for detecting a vibration of the vibrating body, and used, for example, in a navigation system of an automobile or for protecting an unsteady hold on a video-camera and so on.
2. Description of the Prior Art
In this kind of conventional vibrating gyroscope, a vibration is given to a vibrating body. In this state, sine-wave signals having a substantially same strength are output from two detecting piezoelectric elements. When rotating about an axis of the vibrating body, a vibrating direction of the vibrating body is changed by a Coriolis force, the output signal voltage from one detecting piezoelectric element becomes larger and the output signal voltage from the other detecting piezoelectric element becomes smaller responsive to the rotational angular velocity. And hence, by a voltage difference of the output signals from the two detecting piezoelectric elements, the rotational angular velocity is detected.
In such conventional vibratory gyroscope, though the rotational angular velocity can initially be detected accurately, when the vibrating body has warped by temperature change, for example, a signal having a strength responsive to the warp is added to the output signal of one detecting piezoelectric element and deducted from the output signal of the other piezoelectric element, thus it has a possibility that the rotational angular velocity can not be detected accurately. Warped vibrating body is caused by a machining strain of the vibrating body, a difference in coefficients of linear expansion between the vibrating body and the piezoelectric elements formed thereon, and an inaccurate assembling. As such, in the conventional vibratory gyroscope, it was difficult to decide whether the warped vibrating body is caused by the rotational angular velocity or temperature change.
In order to solve such a problem, it may be considered to provide a heater in the vicinity of the vibrating body to keep temperature of the vibrating body at constant, but in this case, power consumption is worsened, the shape is enlarged and much time is required for stabilization.
Though a circuit for compensating characteristics change due to temperature change has been devised, it is not a conclusive solution because of characteristics differences in every piezoelectric element and the characteristics which can be corrected is limited.